1. Field of Invention
This invention is directed to systems and methods for setting up image on paper registration in a printing device.
2. Description of Related Art
In various reproduction systems, including xerographic printing, the control and registration of the position of imageable surfaces such as photoreceptor belts, intermediate transfer belts, if any, and/or images on such imageable surfaces, and the control and registration of images transferred to and developed on a substrate, such as for example, a sheet of paper, involve both initial and process control methods.
To adjust the registration of images on either or both axes, i.e., the lateral axis and/or the process direction axis, relative to the image bearing surface and to one another, includes adjusting the position or timing of the images being formed on the image bearing surface. That may be done, for example, by controlling the raster output scanner (ROS) imaging system or of any other included latent or visible image forming systems.
Various systems and methods have been developed to control registration of image on paper after an initial registration has been made. Examples of such registration systems include those shown and described in U.S. Pat. Nos. 5,821,971; 5,889,545; 6,137,517; 6,141,464; 6,178,031; and 6,275,244, the subject matter of each patent incorporated herein by reference in its entirety.
U.S. Pat. No. 5,642,202, the subject matter of which is incorporated herein by reference in its entirety, discloses a process for initial registration calibration of a printing system including a printer and a master test image document printed by the printer.
There are a number of sources of image on sheet (IOS) or image on paper (IOP) registration errors which may be addressed, including process magnification, lateral magnification, lateral margin shifts, process margin shifts, paper skew and/or imager skew. Process magnification is the magnification of the image in the process direction, i.e., the direction in which the substrate onto which the image is transferred and developed moves through the image transfer and developing apparatus. Lateral magnification is the magnification of the image in the lateral direction, i.e., in the direction substantially perpendicular to the process direction. Paper skew is the angular deviation of the longitudinal axis of the substrate in the process direction and/or the angular deviation of the lateral axis of the substrate perpendicular to the process direction. Imager skew is the angular deviation of the raster output scanner scan lines from the process direction or a line normal to the process direction.
The lateral margins are the spaces between each edge of the image transferred to and developed on the substrate and each adjacent edge of the substrate which is substantially parallel to the process direction. The process margins are the spaces between each edge of the image transferred to and developed on the substrate and each adjacent edge of the substrate which is substantially perpendicular to the process direction. It should be noted that, in many xerographic image forming devices, each image is exposed successively by one or more raster output scanner imagers. Each raster output scanner has a start of scan (SOS) sensor and an end of scan (EOS) sensor. These sensors, i.e., the start of scan (SOS) and end of scan (EOS) sensors, along with the delay before the first pixel is imaged after the start of scan occurs, and the associated timing of when the start of scan occurs, establish the lateral and process margins of a latent image which is to be developed and transferred to a substrate.
Because the effects of these possible image on sheet or image on paper registration errors are interrelated, conventional image on sheet or image on paper setup/calibration procedures first requires correcting for any paper skew and imager skew errors, then correcting for any lateral and process magnification errors, and then correcting for any lateral and process margin errors.
Each correction step may involve multiple iterations of printing and measuring test images and adjusting imaging system parameters before registration error magnitudes are reduced to acceptable levels. U.S. Pat. No. 4,627,721, the subject matter of which is incorporated herein by reference in its entirety, discloses automatic adjustment of optical components in an optical scanning systems after a technical representative has visually inspected sample copies of a test pattern and entered adjustment numbers at a control console. In one specific embodiment, one sample copy is compared by the technical representative with the test pattern to adjust the magnification setting and a sequence of a set of five copies are produced to allow coarse and fine adjustments to the focus.
This invention provides systems and methods that use an initial set of measurements to determine and reduce each of a number of image on paper registration errors in a single operator step.
This invention separately provides systems and methods that use an initial set of measurements to determine and reduce each of a number of image on paper errors in a single operator step.
This invention separately provides systems and methods that use an initial set of measurements and that compensate for different paper types and sizes.
This invention separately provides systems and methods that use an initial set of measurements to determine and reduce each of a number of image on paper errors in a single operator step and that compensate for different rates of paper shrinkage.
The invention separately provides systems and methods that employ a set of algorithms that uses an initial set of measurements to determine and reduce each of a number of image on paper errors in a single operator step and that compensate for different paper types and sizes.
This invention separately provides systems and methods that employ algorithms that use an initial set of measurements to determine and reduce each of a number of image on paper registration errors in a single operator step.
This invention separately provides systems and methods that employ algorithms that use an initial set of measurements to determine and reduce each of a number of image on paper errors in a single operator step and that compensate for different rates of paper shrinkage.
In various exemplary embodiments of the systems and methods of this invention, a set of measurements is made on a test print and a series of geometrical transformations is made based on the measurements to determine a plurality of registration errors, including one or more of process magnification errors, lateral magnification errors, process margin errors, lateral margin errors, paper skew errors and imager skew errors, which affect image on paper registration.
In various exemplary embodiments of the systems and methods of this invention, the geometrical transformations are performed by algorithms which are shown and described herein. The geometrical transformations are then used to make adjustments to appropriate actuators so that image on sheet (IOS) or image on paper (IOP) registration is within desired specifications. Examples of such actuators include pixel clock frequency, photoreceptor speed, ROS scan lateral margin delay; process direction delays, paper steering systems, etc. The algorithms disclosed in this application may be modified to be used with a variety of printing systems and methods.
In various exemplary embodiments of the systems and methods of the invention, printing system mis-registration adjustments may include adjusting a pixel clock frequency and/or a photoreceptor belt or drum speed, adjusting the first pixel delay after the start of scan (SOS) signal, varying the sheet timing and/or position in the paper path, adjusting the ROS angular position relative to the photoreceptor among other techniques. The incorporated patents indicate several printing parameters which can be varied to achieve proper registration of images on paper. In various exemplary embodiments of the systems and methods of this invention, paper shrink effects on registration can be compensated for using determinations made on a number of different papers, such as, for example, evaluating the same test pattern on different substrates. Moreover, a paper conditioner to pre-shrink or re-wet the paper may be used to compensate for different known substrate shrinkage rates.
In various exemplary embodiments of the systems and methods of this invention, the measurements are made on both sides of a duplex substrate or sheet to optimize image on paper registration for duplex printing.
These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention.